bootconfig: Print array as multiple commands for legacy command line

Print arraied values as multiple same options for legacy
kernel command line. With this rule, if the "kernel.*" and
"init.*" array entries in bootconfig are printed out as
multiple same options, e.g.

kernel {
 console = "ttyS0,115200"
 console += "tty0"
}

will be correctly converted to

console="ttyS0,115200" console="tty0"

in the kernel command line.

Link: http://lkml.kernel.org/r/158220118213.26565.8163300497009463916.stgit@devnote2

Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Author: mhiramat

init/main.c

@@ -268,7 +268,6 @@ static int __init xbc_snprint_cmdline(char *buf, size_t size,
 {
 	struct xbc_node *knode, *vnode;
 	char *end = buf + size;
-	char c = '\"';
 	const char *val;
 	int ret;
 
@@ -279,25 +278,20 @@ static int __init xbc_snprint_cmdline(char *buf, size_t size,
 			return ret;
 
 		vnode = xbc_node_get_child(knode);
-		ret = snprintf(buf, rest(buf, end), "%s%c", xbc_namebuf,
-				vnode ? '=' : ' ');
-		if (ret < 0)
-			return ret;
-		buf += ret;
-		if (!vnode)
+		if (!vnode) {
+			ret = snprintf(buf, rest(buf, end), "%s ", xbc_namebuf);
+			if (ret < 0)
+				return ret;
+			buf += ret;
 			continue;
-
-		c = '\"';
+		}
 		xbc_array_for_each_value(vnode, val) {
-			ret = snprintf(buf, rest(buf, end), "%c%s", c, val);
+			ret = snprintf(buf, rest(buf, end), "%s=\"%s\" ",
+				       xbc_namebuf, val);
 			if (ret < 0)
 				return ret;
 			buf += ret;
-			c = ',';
 		}
-		if (rest(buf, end) > 2)
-			strcpy(buf, "\" ");
-		buf += 2;
 	}
 
 	return buf - (end - size);